// backend/live.go
package main

import (
	"bufio"
	"bytes"
	"context"
	"fmt"
	"io"
	"net/http"
	"net/url"
	"os"
	"os/exec"
	"path"
	"path/filepath"
	"regexp"
	"strings"
	"time"
)

// ============================================================
// HLS Live Preview serving (+ m3u8 rewrite)
// ============================================================
//
// This file contains everything related to the HLS live preview stream:
// - serving index*.m3u8 + segment files from a job's PreviewDir
// - rewriting m3u8 segment URLs to a configurable base path
// - starting/stopping the ffmpeg HLS preview process (per job)
// - hover/play activation checks + preview "touch" + ensure-start logic
//
// It intentionally reuses existing globals/types from your backend (package main):
//   - jobs, jobsMu, RecordJob, JobRunning
//   - ffmpegPath, previewSem
//   - notifyJobsChanged()
//   - assetIDForJob(job *RecordJob) string
//   - startLiveThumbJPGLoop(ctx, job)
// ============================================================

// Allowed files that may be served out of PreviewDir.
var previewFileRe = regexp.MustCompile(`^(index(_hq)?\.m3u8|seg_(low|hq)_\d+\.ts|seg_\d+\.ts|init\.m4s|\w+\.m4s)$`)

func serveLiveNotReady(w http.ResponseWriter, r *http.Request) {
	// ✅ Für HLS-Clients (hls.js) ist 204 beim Manifest "ein Fehler" -> aggressive Retries.
	// Deshalb: IMMER 200 + gültige (aber leere) m3u8 zurückgeben.
	w.Header().Set("Content-Type", "application/vnd.apple.mpegurl; charset=utf-8")
	w.Header().Set("Cache-Control", "no-store")
	w.Header().Set("X-Content-Type-Options", "nosniff")
	w.Header().Set("Retry-After", "1")

	if r.Method == http.MethodHead {
		w.WriteHeader(http.StatusOK)
		return
	}

	body := "#EXTM3U\n" +
		"#EXT-X-VERSION:3\n" +
		"#EXT-X-TARGETDURATION:2\n" +
		"#EXT-X-MEDIA-SEQUENCE:0\n"

	w.WriteHeader(http.StatusOK)
	_, _ = w.Write([]byte(body))
}

func maybeBlockHLSOnPreview(w http.ResponseWriter, r *http.Request, basePath, file string) bool {
	// Nur /api/preview (nicht /api/preview/live)
	if strings.TrimSpace(basePath) != "/api/preview" {
		return false
	}

	low := strings.ToLower(strings.TrimSpace(file))
	if low == "" {
		return false
	}

	// Nur echte HLS-Dateien blocken (Manifest/Segmente)
	if strings.HasSuffix(low, ".m3u8") || strings.HasSuffix(low, ".ts") || strings.HasSuffix(low, ".m4s") {
		w.Header().Set("Cache-Control", "no-store")
		w.Header().Set("X-Preview-HLS-Disabled", "1")

		http.Error(w, "HLS disabled on /api/preview; use /api/preview/live", http.StatusGone) // 410
		return true
	}

	return false
}

// stopPreview stops the running ffmpeg HLS preview process for a job and resets state.
func stopPreview(job *RecordJob) {
	jobsMu.Lock()
	cmd := job.previewCmd
	cancel := job.previewCancel
	job.previewCmd = nil
	job.previewCancel = nil
	job.LiveThumbStarted = false
	job.PreviewDir = ""
	jobsMu.Unlock()

	if cancel != nil {
		cancel()
	}
	if cmd != nil && cmd.Process != nil {
		_ = cmd.Process.Kill()
	}
}

func recordPreviewLive(w http.ResponseWriter, r *http.Request) {
	// ✅ Route bleibt /api/preview/live
	// Wenn kein "file" Parameter da ist, liefern wir den neuen Single-Request Stream (fMP4).
	file := strings.TrimSpace(r.URL.Query().Get("file"))
	if file == "" {
		recordPreviewLiveFMP4(w, r)
		return
	}

	// Legacy: HLS file serving + m3u8 rewrite (falls du es noch irgendwo brauchst)
	id := strings.TrimSpace(r.URL.Query().Get("id"))
	if id == "" {
		http.Error(w, "id fehlt", http.StatusBadRequest)
		return
	}
	servePreviewHLSFileWithBase(w, r, id, file, "/api/preview/live")
}

// recordPreviewFile serves ONLY the HLS file requests for /api/preview?file=...
// preview.jpg bleibt in preview.go (servePreviewJPGAlias).
func recordPreviewFile(w http.ResponseWriter, r *http.Request) {
	if r.Method != http.MethodGet && r.Method != http.MethodHead {
		http.Error(w, "method not allowed", http.StatusMethodNotAllowed)
		return
	}

	id := strings.TrimSpace(r.URL.Query().Get("id"))
	if id == "" {
		id = strings.TrimSpace(r.URL.Query().Get("name"))
	}
	if id == "" {
		http.Error(w, "id fehlt", http.StatusBadRequest)
		return
	}

	file := strings.TrimSpace(r.URL.Query().Get("file"))
	if file == "" {
		http.Error(w, "file fehlt", http.StatusBadRequest)
		return
	}

	// ✅ HLS auf /api/preview blocken (Manifest/Segmente), um Polling-Storm zu verhindern.
	// Wenn du es NICHT blocken willst, diese if-Zeile entfernen.
	if maybeBlockHLSOnPreview(w, r, "/api/preview", file) {
		return
	}

	// Alles andere (falls doch erlaubt) über die gemeinsame Serving-Funktion
	servePreviewHLSFileWithBase(w, r, id, file, "/api/preview")
}

// servePreviewHLSFileWithBase serves a single HLS file (index/segment) for a job.
// If it's an m3u8, it is rewritten so that segment URIs point at basePath.
func servePreviewHLSFileWithBase(w http.ResponseWriter, r *http.Request, id, file, basePath string) {
	file = strings.TrimSpace(file)
	if file == "" || filepath.Base(file) != file || !previewFileRe.MatchString(file) {
		http.Error(w, "ungültige file", http.StatusBadRequest)
		return
	}

	isIndex := file == "index.m3u8" || file == "index_hq.m3u8"

	jobsMu.Lock()
	job, ok := jobs[id]
	state := ""
	if ok && job != nil {
		state = strings.TrimSpace(job.PreviewState)
	}
	jobsMu.Unlock()

	// HEAD: quick existence check
	if r.Method == http.MethodHead {
		if !ok || job == nil {
			w.WriteHeader(http.StatusNotFound)
			return
		}
		if state == "private" {
			w.WriteHeader(http.StatusForbidden)
			return
		}
		if state == "offline" {
			w.WriteHeader(http.StatusNotFound)
			return
		}
		previewDir := strings.TrimSpace(job.PreviewDir)
		if previewDir == "" {
			w.WriteHeader(http.StatusNotFound)
			return
		}
		p := filepath.Join(previewDir, file)
		if st, err := os.Stat(p); err == nil && !st.IsDir() {
			w.Header().Set("Cache-Control", "no-store")
			w.WriteHeader(http.StatusOK)
			return
		}
		w.WriteHeader(http.StatusNotFound)
		return
	}

	// activation: hover or play=1
	active := isHover(r) || strings.TrimSpace(r.URL.Query().Get("play")) == "1"
	if !active {
		if isIndex {
			serveLiveNotReady(w, r)
			return
		}
		http.Error(w, "preview not active", http.StatusNotFound)
		return
	}

	if !ok || job == nil {
		if isIndex {
			serveLiveNotReady(w, r)
			return
		}
		http.Error(w, "job nicht gefunden", http.StatusNotFound)
		return
	}

	ensurePreviewStarted(r, job)
	touchPreview(job)

	jobsMu.Lock()
	state = strings.TrimSpace(job.PreviewState)
	jobsMu.Unlock()

	if state == "private" {
		http.Error(w, "model private", http.StatusForbidden)
		return
	}
	if state == "offline" {
		http.Error(w, "model offline", http.StatusNotFound)
		return
	}
	if state == "error" {
		http.Error(w, "preview error", http.StatusServiceUnavailable)
		return
	}

	previewDir := strings.TrimSpace(job.PreviewDir)
	if previewDir == "" {
		if isIndex {
			serveLiveNotReady(w, r)
			return
		}
		http.Error(w, "preview nicht verfügbar", http.StatusNotFound)
		return
	}

	p := filepath.Join(previewDir, file)
	st, err := os.Stat(p)
	if err != nil || st.IsDir() {
		if isIndex {
			serveLiveNotReady(w, r)
			return
		}
		http.Error(w, "datei nicht gefunden", http.StatusNotFound)
		return
	}

	ext := strings.ToLower(filepath.Ext(p))
	w.Header().Set("Cache-Control", "no-store")
	w.Header().Set("X-Accel-Buffering", "no")

	// m3u8 -> rewrite
	if ext == ".m3u8" {
		raw, err := os.ReadFile(p)
		if err != nil {
			http.Error(w, "m3u8 read failed", http.StatusInternalServerError)
			return
		}
		rewritten := rewriteM3U8WithBase(raw, id, basePath)
		w.Header().Set("Content-Type", "application/vnd.apple.mpegurl; charset=utf-8")
		w.WriteHeader(http.StatusOK)
		_, _ = w.Write(rewritten)
		return
	}

	switch ext {
	case ".ts":
		w.Header().Set("Content-Type", "video/mp2t")
	case ".m4s":
		w.Header().Set("Content-Type", "video/iso.segment")
	default:
		w.Header().Set("Content-Type", "application/octet-stream")
	}

	// segments may still be written -> wait until size stabilizes
	if ext == ".ts" || ext == ".m4s" {
		if !waitForStableFile(p, 2, 120*time.Millisecond) {
			http.Error(w, "segment not ready", http.StatusNotFound)
			return
		}
	}

	f, err := os.Open(p)
	if err != nil {
		http.Error(w, "open failed", http.StatusNotFound)
		return
	}
	defer f.Close()

	http.ServeContent(w, r, file, st.ModTime(), f)
}

func waitForStableFile(path string, checks int, interval time.Duration) bool {
	var last int64 = -1
	for i := 0; i < checks; i++ {
		st, err := os.Stat(path)
		if err != nil || st.IsDir() {
			return false
		}
		sz := st.Size()
		if last >= 0 && sz == last {
			return true
		}
		last = sz
		time.Sleep(interval)
	}
	return false
}

func classifyPreviewFFmpegStderr(stderr string) (state string, httpStatus int) {
	s := strings.ToLower(stderr)
	if strings.Contains(s, "403 forbidden") || strings.Contains(s, "http error 403") || strings.Contains(s, "server returned 403") {
		return "private", http.StatusForbidden
	}
	if strings.Contains(s, "404 not found") || strings.Contains(s, "http error 404") || strings.Contains(s, "server returned 404") {
		return "offline", http.StatusNotFound
	}
	return "", 0
}

// startPreviewHLS starts ffmpeg to generate HLS segments in previewDir.
// It also starts your existing live-thumb loop: startLiveThumbJPGLoop(ctx, job).
func startPreviewHLS(ctx context.Context, job *RecordJob, m3u8URL, previewDir, httpCookie, userAgent string) error {
	if strings.TrimSpace(ffmpegPath) == "" {
		return fmt.Errorf("kein ffmpeg gefunden – setze FFMPEG_PATH oder lege ffmpeg(.exe) neben das Backend")
	}
	if err := os.MkdirAll(previewDir, 0o755); err != nil {
		return err
	}

	jobsMu.Lock()
	job.PreviewState = ""
	job.PreviewStateAt = ""
	job.PreviewStateMsg = ""
	hidden := job.Hidden
	jobsMu.Unlock()

	if !hidden {
		publishJobUpsert(job)
	}

	commonIn := []string{"-y"}
	if strings.TrimSpace(userAgent) != "" {
		commonIn = append(commonIn, "-user_agent", userAgent)
	}
	if strings.TrimSpace(httpCookie) != "" {
		commonIn = append(commonIn, "-headers", fmt.Sprintf("Cookie: %s\r\n", httpCookie))
	}
	commonIn = append(commonIn, "-i", m3u8URL)

	hqArgs := append(commonIn,
		"-vf", "scale=480:-2",
		"-c:v", "libx264", "-preset", "veryfast", "-tune", "zerolatency",
		"-pix_fmt", "yuv420p",
		"-profile:v", "main",
		"-level", "3.1",
		"-threads", "4",
		"-g", "48", "-keyint_min", "48", "-sc_threshold", "0",
		"-map", "0:v:0",
		"-map", "0:a:0?",
		"-c:a", "aac", "-b:a", "128k", "-ac", "2",
		"-f", "hls",
		"-hls_time", "2",
		"-hls_list_size", "6",
		"-hls_allow_cache", "0",
		"-hls_flags", "delete_segments+append_list+independent_segments+temp_file",
		"-hls_segment_filename", filepath.Join(previewDir, "seg_hq_%05d.ts"),
		filepath.Join(previewDir, "index_hq.m3u8"),
	)

	cmd := exec.CommandContext(ctx, ffmpegPath, hqArgs...)
	var stderr bytes.Buffer
	cmd.Stderr = &stderr

	jobsMu.Lock()
	job.previewCmd = cmd
	jobsMu.Unlock()

	go func() {
		if err := previewSem.Acquire(ctx); err != nil {
			jobsMu.Lock()
			if job.previewCmd == cmd {
				job.previewCmd = nil
			}
			jobsMu.Unlock()
			return
		}
		defer previewSem.Release()

		if err := cmd.Run(); err != nil && ctx.Err() == nil {
			st := strings.TrimSpace(stderr.String())
			state, code := classifyPreviewFFmpegStderr(st)

			jobsMu.Lock()
			if state != "" {
				job.PreviewState = state
				job.PreviewStateAt = time.Now().UTC().Format(time.RFC3339Nano)
				job.PreviewStateMsg = fmt.Sprintf("ffmpeg input returned HTTP %d", code)
			} else {
				job.PreviewState = "error"
				job.PreviewStateAt = time.Now().UTC().Format(time.RFC3339Nano)
				if len(st) > 280 {
					job.PreviewStateMsg = st[:280] + "…"
				} else {
					job.PreviewStateMsg = st
				}
			}
			hidden := job.Hidden
			jobsMu.Unlock()

			if !hidden {
				publishJobUpsert(job)
			}

			//fmt.Printf("⚠️  preview hq ffmpeg failed: %v (%s)\n", err, st)
		}

		jobsMu.Lock()
		if job.previewCmd == cmd {
			job.previewCmd = nil
		}
		jobsMu.Unlock()
	}()

	startLiveThumbJPGLoop(ctx, job)
	return nil
}

// rewriteM3U8WithBase rewrites all segment URIs inside an m3u8 to point at basePath.
//
// Example output line:
//
//	/api/preview/live?id=<id>&file=seg_hq_00001.ts&play=1
func rewriteM3U8WithBase(raw []byte, id string, basePath string) []byte {
	basePath = strings.TrimSpace(basePath)
	if basePath == "" {
		basePath = "/api/preview"
	}
	if !strings.HasPrefix(basePath, "/") {
		basePath = "/" + basePath
	}

	base := basePath + "?id=" + url.QueryEscape(id) + "&file="

	var out bytes.Buffer
	sc := bufio.NewScanner(bytes.NewReader(raw))
	for sc.Scan() {
		line := sc.Text()
		trim := strings.TrimSpace(line)
		if trim == "" {
			out.WriteByte('\n')
			continue
		}

		// tags: may contain URI="..."
		if strings.HasPrefix(trim, "#") {
			line = rewriteAttrURIWithBase(line, base, basePath)
			out.WriteString(line)
			out.WriteByte('\n')
			continue
		}

		u := trim

		// absolute URLs: keep
		if strings.HasPrefix(u, "http://") || strings.HasPrefix(u, "https://") {
			out.WriteString(line)
			out.WriteByte('\n')
			continue
		}

		// already points to our endpoint: keep
		if strings.Contains(u, basePath) || strings.Contains(u, "/api/preview") {
			out.WriteString(line)
			out.WriteByte('\n')
			continue
		}

		name := path.Base(u)
		out.WriteString(base + url.QueryEscape(name) + "&play=1")
		out.WriteByte('\n')
	}
	if err := sc.Err(); err != nil {
		return raw
	}
	return out.Bytes()
}

func rewriteAttrURIWithBase(line, base string, basePath string) string {
	const key = `URI="`
	i := strings.Index(line, key)
	if i < 0 {
		return line
	}
	j := strings.Index(line[i+len(key):], `"`)
	if j < 0 {
		return line
	}
	start := i + len(key)
	end := start + j
	val := line[start:end]
	valTrim := strings.TrimSpace(val)

	// keep absolute or already-rewritten URIs
	if strings.HasPrefix(valTrim, "http://") || strings.HasPrefix(valTrim, "https://") {
		return line
	}
	if strings.Contains(valTrim, basePath) || strings.Contains(valTrim, "/api/preview") {
		return line
	}

	name := path.Base(valTrim)
	repl := base + url.QueryEscape(name) + "&play=1"
	return line[:start] + repl + line[end:]
}

// isHover decides whether this request should count as "active".
func isHover(r *http.Request) bool {
	v := strings.ToLower(strings.TrimSpace(r.URL.Query().Get("hover")))
	return v == "1" || v == "true" || v == "yes"
}

// touchPreview updates the last-hit timestamp so your cleanup/stop logic can use it.
func touchPreview(job *RecordJob) {
	if job == nil {
		return
	}
	jobsMu.Lock()
	job.previewLastHit = time.Now()
	jobsMu.Unlock()
}

// ensurePreviewStarted starts the ffmpeg HLS preview if not running yet.
func ensurePreviewStarted(r *http.Request, job *RecordJob) {
	if job == nil {
		return
	}
	job.previewStartMu.Lock()
	defer job.previewStartMu.Unlock()

	jobsMu.Lock()
	if job.previewCmd != nil && job.PreviewDir != "" {
		job.previewLastHit = time.Now()
		jobsMu.Unlock()
		return
	}
	m3u8 := strings.TrimSpace(job.PreviewM3U8)
	cookie := strings.TrimSpace(job.PreviewCookie)
	ua := strings.TrimSpace(job.PreviewUA)
	jobsMu.Unlock()

	if m3u8 == "" {
		return
	}

	pctx, cancel := context.WithCancel(context.Background())
	assetID := assetIDForJob(job)
	pdir := filepath.Join(os.TempDir(), "rec_preview", assetID)

	jobsMu.Lock()
	job.PreviewDir = pdir
	job.previewCancel = cancel
	job.previewLastHit = time.Now()
	jobsMu.Unlock()

	_ = startPreviewHLS(pctx, job, m3u8, pdir, cookie, ua)
}

// ============================================================
// Live fMP4 (single request, chunked) via ffmpeg -> stdout
// Route: /api/preview/live-fmp4?id=<jobId>&hover=1
// ============================================================

func recordPreviewLiveFMP4(w http.ResponseWriter, r *http.Request) {
	if r.Method != http.MethodGet {
		http.Error(w, "Nur GET erlaubt", http.StatusMethodNotAllowed)
		return
	}

	id := strings.TrimSpace(r.URL.Query().Get("id"))
	if id == "" {
		http.Error(w, "id fehlt", http.StatusBadRequest)
		return
	}

	// activation: hover or play=1 (wie bei HLS)
	active := isHover(r) || strings.TrimSpace(r.URL.Query().Get("play")) == "1"
	if !active {
		http.Error(w, "preview not active", http.StatusNotFound)
		return
	}

	jobsMu.Lock()
	job, ok := jobs[id]
	state := ""
	if ok && job != nil {
		state = strings.TrimSpace(job.PreviewState)
	}
	jobsMu.Unlock()

	if !ok || job == nil {
		http.Error(w, "job nicht gefunden", http.StatusNotFound)
		return
	}

	username := extractUsername(job.SourceURL)
	if strings.TrimSpace(username) != "" {
		cookie := strings.TrimSpace(job.PreviewCookie)
		ua := strings.TrimSpace(job.PreviewUA)
		if ua == "" {
			ua = "Mozilla/5.0"
		}

		ctxRefresh, cancelRefresh := context.WithTimeout(r.Context(), 8*time.Second)
		newHls, err := fetchCurrentBestHLS(ctxRefresh, username, cookie, ua)
		cancelRefresh()

		if err == nil && strings.TrimSpace(newHls) != "" {
			jobsMu.Lock()
			oldHls := strings.TrimSpace(job.PreviewM3U8)
			job.PreviewM3U8 = strings.TrimSpace(newHls)
			job.PreviewCookie = cookie
			job.PreviewUA = ua
			job.PreviewState = ""
			job.PreviewStateAt = ""
			job.PreviewStateMsg = ""
			jobsMu.Unlock()

			if oldHls != "" && oldHls != strings.TrimSpace(newHls) {
				stopPreview(job)
			}
		}
	}

	// ensure ffmpeg preview input data exists
	// (PreviewM3U8 + Cookie/UA werden beim Job gesetzt)
	m3u8 := strings.TrimSpace(job.PreviewM3U8)
	if m3u8 == "" {
		http.Error(w, "preview m3u8 fehlt", http.StatusNotFound)
		return
	}

	// states
	if state == "private" {
		http.Error(w, "model private", http.StatusForbidden)
		return
	}
	if state == "offline" {
		http.Error(w, "model offline", http.StatusNotFound)
		return
	}
	if state == "error" {
		http.Error(w, "preview error", http.StatusServiceUnavailable)
		return
	}

	// Headers: fMP4 stream
	w.Header().Set("Content-Type", `video/mp4`)
	w.Header().Set("Cache-Control", "no-store")
	w.Header().Set("X-Accel-Buffering", "no")

	// Sehr wichtig: Flushbar?
	flusher, okf := w.(http.Flusher)
	if !okf {
		http.Error(w, "Streaming nicht unterstützt", http.StatusInternalServerError)
		return
	}

	// Client disconnect => ffmpeg stoppen
	ctx := r.Context()

	// Cookie/UA aus Job
	cookie := strings.TrimSpace(job.PreviewCookie)
	ua := strings.TrimSpace(job.PreviewUA)
	if ua == "" {
		ua = "Mozilla/5.0"
	}

	// ffmpeg args: input = m3u8, output = fragmented mp4 to stdout
	// ✅ Video + Audio für Browser-Playback
	args := []string{"-hide_banner", "-loglevel", "error"}
	if ua != "" {
		args = append(args, "-user_agent", ua)
	}
	if cookie != "" {
		args = append(args, "-headers", fmt.Sprintf("Cookie: %s\r\n", cookie))
	}

	// Input
	args = append(args, "-i", m3u8)

	// Video + Audio encode (low-latency-ish)
	args = append(args,
		"-map", "0:v:0",
		"-map", "0:a:0?",
		"-vf", "scale=480:-2",
		"-c:v", "libx264",
		"-preset", "veryfast",
		"-tune", "zerolatency",
		"-pix_fmt", "yuv420p",
		"-profile:v", "main",
		"-level", "3.1",
		"-g", "48",
		"-keyint_min", "48",
		"-sc_threshold", "0",
		"-c:a", "aac",
		"-b:a", "128k",
		"-ac", "2",
		"-ar", "48000",
	)

	// Output: fMP4 fragmented to stdout (single HTTP response)
	args = append(args,
		"-f", "mp4",
		"-movflags", "frag_keyframe+empty_moov+default_base_moof",
		"-frag_duration", "2000000", // 2s (µs)
		"-min_frag_duration", "2000000",
		"pipe:1",
	)

	cmd := exec.CommandContext(ctx, ffmpegPath, args...)

	// stdout -> response
	stdout, err := cmd.StdoutPipe()
	if err != nil {
		http.Error(w, "ffmpeg stdout pipe failed", http.StatusInternalServerError)
		return
	}

	// stderr nur für Debug (optional)
	var stderr bytes.Buffer
	cmd.Stderr = &stderr

	// Start
	if err := cmd.Start(); err != nil {
		http.Error(w, "ffmpeg start failed: "+err.Error(), http.StatusInternalServerError)
		return
	}

	// Wenn Client weg => Prozess killt CommandContext sowieso (ctx cancels),
	// aber wir kopieren streaming-mäßig.
	buf := make([]byte, 32*1024)

	for {
		select {
		case <-ctx.Done():
			_ = cmd.Process.Kill()
			return
		default:
		}

		n, rerr := stdout.Read(buf)
		if n > 0 {
			_, _ = w.Write(buf[:n])
			flusher.Flush()
		}
		if rerr != nil {
			if rerr == io.EOF {
				break
			}
			break
		}
	}

	// Wait (verhindert Zombies)
	_ = cmd.Wait()
}